Dive planning for closed circuit rebreather

This misses a single issue to be used as a base for further discussion:
The CC setpoint is used for the next segment, not the one specified for. I
also have in mind to modify the existing code to use setpoints specified
in mbar and plain integer instead of float values.

Signed-off-by: Jan Schubert <Jan.Schubert@GMX.li>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Make dive planner more useful for closed circuit diving

Add a sample at time 0 to allow for a pO2 from the start of the dive.
Remember the last pO2 so it doesn't have to be repeated (and the right
thing happens for the planned part of the dive).

This still doesn't allow us to change the setpoint at a certain depth
(which would be analogous to being able to switch to a certain gas at a
certain depth in OC plans), but with this commit it's already usable.

This commit also fixes a couple of small bugs in commit b8ee3de870fa
("Dive planning for closed circuit rebreather") where a pO2 of 1.1 was
hardcoded in one place, throwing off all plan calculations and integer
math was used to calculate a floating point value (leading to most pO2
values actually used being 1.0).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Be even more permissive in our date parsing logic

Not that we aren't already insanely permissive in parsing just about any
random noise that could _possibly_ be construed as xml and turn it into
a dive, this makes us even laxer.

If somebody wants to have a <date> tag with both date and time, why the
heck not? It's fine.  And if it has just the date, that's fine too.  And
the date can be in any of several formats.  We really don't care, the
more permissive, the better.

We strive to always write beautiful xml, but let's face it, not
everybody else does.  If we can turn random line noise into a dive, we
should do so.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
xml-parsing: accept 'sitelat' and 'sitelon' for GPS coordinates

Are they ugly and insane tags? Yes.  Are they used? Bingo.  MacDive uses
this lovely format for specifying dive site location.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
parse-xml: allow XML nodes with empty tag names

They happen for CDATA content, where libxml2 turns the CDATA fields into
a child of the parent entry, but without a name.

Now, of course, any sane person would just want to use the CDATA as the
string value of the parent itself, but libxml2 probably does this
insanity for a reason.  And the reason is probably that some misguided
people want to *write* XML using libxml2, and then the stupid child node
actually acts as a "now I want you to write this data as CDATA".

Whatever the reason, let's just ignore it.  We will just traverse such a
nameless child and be happy, and we'll give the nameless child the name
of the parent.  Our XML node matching logic will then never see this
insane nameless child at all, and doesn't have to care.

Our whole XML parsing rule-of-thumb is to take the whole "be strict in
what you output, but generous in what you accept" to its logical
conclusion.  Because we will literally accept almost anything, in any
format.  You can mix tags or attributes wildly, and youc an use CDATA or
not as you see fit.  We just don't care.

We're the honeybadger of the divelog world.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Merge branch 'cc-plan'

Add the ability to plan closed circuit (rebreather) dives